In the case of press rolls the requirement is generally justly made that a constant line pressure can be set over the entire width of a roll gap in a wide line pressure range. Such conditions are required by the paper, textile, plastic and other industries, because non-uniform line pressures in the pressing gap can very easily reduce the quality of the product and impair the productivity of the machines. However, it is very difficult to maintain these conditions because these rolls which rotate on bearings outside the roll body elastically bend in the direction of the resultant external forces and therefore a uniform line pressure is only possible if very strictly defined conditions are fulfilled; otherwise special precautions must be taken. The requirement that the line pressures must be adjustable within a wide range are not fulfilled by the presently known constructional solution.
German Offenlegungsschriften 1,940,175 discloses a structure in which a roll for the pressure treatment of flat materials has a roll core, a cylindrical roll shell coaxial thereto and inflating members which can be filled with pressure medium located between the same, with the inflating members being constructed as sealable chambers surrounding the roll core, and wherein the roll shell and roll core can be rotated in the same direction and with substantially the same angular velocity. A disadvantage of this construction is that in the case of a change of the contact surface of the inflating members, the vertical bearing capacity thereof also changes.